Timothy M. Caldwell, who unsuccessfully ran for a seat on the Board of Selectmen in a special election last June, has taken out papers to run for a seat on the board in this spring’s annual town election. Caldwell lost by about 100 votes to William Cranshaw. Incumbent selectman David Gavin has also taken out nomination papers for the election. In addition to two seats on the Board of Selectmen, the May 6 ballot will include two seats on the School Committee, a seat on the Library Board of Trustees, and the town moderator position. The last day to obtain nomination papers from the town clerk’s office is March 14.